Yes.
Ball pythons need a form of belly heat to properly digest their food. They will not bask in the heat lamp and will loose proper heat for digestion through hiding (which all balls need to do to be stress-free).
They need a good heat gradient (warm side 90-95F and cool side 80-85F) which is nearly impossible with out a UTH.

Heat lamps also suck out desired humidity from a bps tank. I recommend using a good UTH with a thermostat (you need something to control it) for a ball python with no heat lamp. A viewing lamp is fine if there is low wattage bulb and it's turned off at night.